Method for manufacturing 3-nitro-1,2,4-triazol-5-one

ABSTRACT

A process for preparing 3-nitro-1,2,4-triazol-5-one by nitrating  1,2,4-trol-5-one in 70% nitric acid at a temperature of from 60° C. to 75° C. and then crystallizing out the product 3-nitro-1,2,4-triazol-5-one at a temperature of from 0° C. to 10° C. The nitro-1,2,4-triazol-5-one is useful as an explosive.

BACKGROUND OF THE INVENTION

This invention relates to heterocylic organic explosives and moreparticularly to nitrated triazoles.

Two methods of manufacturing 3-nitro-1,2,4-triazol-5-one (NTO) currentlyexist. One method used by Los Alamos National Laboratory involves adding70% nitric acid and 1,2,4-triazol-5-one (TO) together at roomtemperature. The mixture is heated until the reaction begins toexotherm. The reactor is then allowed to self-heat until the reaction iscomplete. Yield based on the starting amount of 1,2,4-triazol-5-one is65%. Disadvantages of this process include low yields and unsafeconditions caused by allowing the reactor to self-heat. Scale-up of thistechnique would be especially dangerous because of the difficultiesinvolved in controlling the temperature and the possibility of a runawayreaction and potential fume off.

In the second prior art procedure, the French (SNPE) add1,2,4-triazol-5-one to 98% nitric acid at 0° to 10° C. over a period oftwo hours. The reaction is held at this temperature for 3 hours. Wateris then added to the reactor and the mixture is held for 12 hours.Disadvantages of the SNPE process are the longer reaction time, thelower yield, and the dangers associated with high acid concentrations

SUMMARY OF THE INVENTION

Accordingly, an object of this invention is to provide a new method ofpreparing 3-nitro-1,2,4-triazol-5-one.

Another object of this invention is to provide a new method of preparing3-nitro-1,2,4-triazol-5-one in greater yield.

A further object of this invention is to provide a safer method ofproducing 3-nitro-1,2,4-triazol-5-one.

Yet another object of this invention is to provide a continuous processfor producing 3-nitro-1,2,4-triazol-5-one.

This and other objects of this invention are achieved by providing:

A method of producing 3-nitro-1,2,4-triazol-5-one comprising:

(1) adding 1,2,4-triazol-5-one to 70% nitric acid at a temperature offrom 60° C. to 75° C. until the molar ratio of the 1,2,4-triazole-5-oneadded to the nitric acid is from 1:8 to 1:4;

(2) holding the mixture formed in step (1) at a temperature of from 60°C. to 75° C. until the 1,2,4-triazol-5-one has been nitrated to form3-nitro-1,2,4-triazol-5-one;

(3) cooling the mixture formed in step (2) to a temperature of from 0°C. to 10° C. to crystallize out the 3-nitro-1,2,4-triazol-5-one; and

(4) isolating the product 3-nitro-1,2,4-triazol-5-one.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

This invention may be used either as a batch or as a continuous processto form 3-nitro-1,2,4-triazol-5-one (NTO) from 1,2,4-triazol-5-one (TO)by nitration. In the batch process, 70 percent nitric acid is heated toa temperature in the range of from 60° to 75° C., preferably from 65° C.to 70° C. Then 1,2,4-triazol-5-one is added slowly to maintain thereaction temperature in the range of from 60° C. to 75° C., preferablyfrom 65° C. to 70° C., until the molar ratio of the 1,2,4-triazol-5-oneadded to the nitric acid present is from 1:8 to 1:4, preferably from 1:7to 1:5, and more preferably about 1:6. This addition will generally takefrom about 1 to 2 hours. After the addition is completed the temperatureof the reaction mixture is maintained at 60° C. to 75° C., preferablyfrom 65° C. to 70° C., for about an additional hour to insure completionof the nitration reaction.

The reaction batch is then cooled to a temperature of from 0° C. to 10°C. to cause the product 3-nitro-1,2,4-triazol-5-one to crystallize out.The 3-nitro-1,2,4-triazol-5-one is then separated (e.g., filtered) fromthe solution.

The process may also be run as a continuous process. As in the batchprocess, 70 percent nitric acid is heated in the reactor to atemperature in the range of from 60° C. to 75° C., preferably from 65°C. to 70° C. Then 1,2,4-triazol-5-one is added slowly to maintain thereaction temperature in the range of from 60° C. to 75° C., preferablyfrom 65° C. to 70° C., until the molar ratio of the 1,2,4-triazol-5-oneadded to the nitric acid is from 1:8 to 1:4, preferably from 1:7 to 1:5,and more preferaby about 1:6. Once the reactor is charged in thismanner, 1,2,4-triazol-5-one and 70% nitric acid are continuously addedto the reactor in the same molar ratio as was used to charge it. Thismay be done as a feed solution of 1,2,4-triazol-5-one dissolved in thenitric acid. However, there is a danger of "fume off" occurring whilethe 1,2,4-triazol-5-one is being dissolved in the 70% nitric acid.Therefore, the 1,2,4-triazol-5-one and nitric acid are preferably addedas separate feeds with a dry solids feeder being used to add the1,2,4-triazol-5-one. At the same time, a product stream is drawn fromthe reactor at a rate of flow equal to the rate of flow of the feedsolution. The rate of flow is adjusted to cause a complete turn over orchange of the reactor contents every 2 to 10 hours. During the processthe reaction mixture is maintained at a temperature of from 60° C. to75° C., preferably from 65° C. to 70° C.

The product stream from the reactor is cooled down to from 0° C. to 10°C. and the product crystals of 3-nitro-1,2,4-triazol-5-one are thenseparated (e.g., filtered) from the acid solution.

The general nature of the invention having been set forth, the followingexamples are presented as specific illustrations thereof. It will beunderstood that the invention is not limited to these specific examplesbut is susceptible to various modifications that will be recognized byone of ordinary skill in the art.

EXAMPLE 1 Batch Process

In a 12 liter flask 6.67 L of 70% nitric acid was heated to 65° C. Withagitation, 1.484 kg of 1,2,4-triazol-5-one was added stepwise over aperiod of about 1.0 hour to the preheated nitric acid. The reactiontemperature was maintained between 65° C. and 70° C. for an additionalhour. The 3-nitro-1,2,4-triazol-5-one product and acid mixture wascooled to 10° C. and filtered. The yield based on the starting amount of1,2,4-triazol-5-one was 90%.

EXAMPLE 2 Continuous Process

In a 12 liter flask (reactor) 6.67 L of 70% nitric acid was heated to65°-70° C. With agitation, 1.484 kg of 1,2,4-triazol-5-one was addedstepwise over a period of 1.0 to 1.5 hours. Nitric acid, 70%, was pumpedinto the reactor at a rate of 6.672 liters/four hours and 1.484kg1,2,4-triazol-5-one was also added over a four hour period using a drysolids feeder. The temperature of the mixture in the reactor wasmaintained at 65°-70° C. An equal flow rate was pumped from the reactorto a crystallizer where the nitric acid and 3-nitro-1,2,4-triazol-5-onemixture was cooled down to 10° C. and then pumped through a filter.After filtering, the product 3-nitro-1,2,4-triazol-5-one was dried andweighed, the yield based on the starting amount of 1,2,4-triazol-5-onewas 83%.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims theinvention may be practiced otherwise than as specifically describedherein.

What is claimed is:
 1. A process for producing3-nitro-1,2,4-triazol-5-one comprising(1) adding 1,2,4-triazol-5-one to70% nitric acid at a temperature of from 60° C. to 75° C. until themolar ratio of the 1,2,4-triazol-5-one added to the nitric acid is from1:8 to 1:4; (2) holding the mixture formed in step (1) at a temperatureof from 60° C. to 75° C. until the 1,2,4-triazol-5-one has been nitratedto form 3-nitro-1,2,4-triazol-5-one; (3) cooling the mixture formed instep (2) to a temperature of from 0° C. to 10° C. to crystallize out the3-nitro-1,2,4-triazol-5-one; and (4) isolating the product3-nitro-1,2,4-triazol-5-one.
 2. The process of claim 1 wherein themixtures in steps (1) and (2) are agitated.
 3. The process of claim 1wherein the molar ratio of 1,2,4-triazol-5-one to nitric acid is from1:7 to 1:5.
 4. The process of claim 3 wherein the molar ratio of1,2,4-triazol-5-one to nitric acid is about 1:6.
 5. The process of claim1 wherein the temperature used in steps (1) and (2) is from 65° C. to70° C.
 6. A continuous process for producing 3-nitro-1,2,4-triazol-5-onecomprising(1) charging a reactor by adding 1,2,4-triazol-5-one to 70%nitric acid at a temperature of from 60° C. to 75° C. until the molarratio of the 1,2,4-triazol-5-one added to the nitric acid is from 1:8 to1:4; (2) continuously feeding 1,2,4-triazol-5-one and nitric acid intothe reactor in the same molar ratio as was used to charge the reactor instep (1) while maintaining the reactor temperature in the range of from60° C. to 75° C.; (3) Continuously drawing off a product stream from thereactor; (4) cooling the product stream to from 0° C. to 10° C. tocrystallize out the product 3-nitro-1,2,4-triazol-5-one; and (5)isolating the product 3-nitro-1,2,4-triazol-5-one; provided that therates of flow of the feed and the product streams are adjusted tocompletely change the contents of the reactor every 2 to 10 hours. 7.The process of claim 6 wherein the reaction mixture is agitated.
 8. Theprocess of claim 6 wherein the molar ratio of 1,2,4-triazol-5-one tonitric acid is from 1:7 to 1:5.
 9. The process of claim 8 wherein themolar ratio of 1,2,4-triazol-5-one to nitric acid is about 1:6.
 10. Theprocess of claim 6 wherein the temperature used in steps (1) and (2) isin the range of from 65° C. to 70° C.
 11. The process of claim 6 whereinin step (2) the nitric acid and the 1,2,4-triazol-5-one are fed inseparately.
 12. The process of claim 6 wherein the rates of flow of thefeed and the product streams are adjusted to completely change thecontents of the reactor every 2 to 6 hours.